Security Access Control is out of control after devices over 20-30

Hi, Netgear:

I met big problem about access control when it is turned on.

I turned on access control, and checked "Block all new devices from connecting"

Block function is worked, but after 20 - 30 clients connected, I make some clients to "allowed". but it cannot be "allowed", and when I reboot device, some "ever allowed" clients change to blocked. and I also observed the access control menu is always refreshing and become slower, very hard to show this page.

When saw this symptom , I found another issues is that all buttons cannot be controled. 

To fix this problem, I need to factory reset to make it recover, but when all clients are relogin, this symptom is happened again.

Please kindly fix it, I listed device info here.

Thanks,

Howard.